Prazosin is in a group of drugs called alpha-adrenergic (AL-fa ad-ren-ER-jik) blockers. Prazosin relaxes your veins and arteries so that blood can more easily pass through them.

Prazosin is used to treat hypertension (high blood pressure).

Prazosin may also be used for other purposes not listed in this medication guide.

INSTRUCTIONS

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Your doctor may occasionally change your dose to make sure you get the best results. Prazosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it or whenever your dose is changed. Call your doctor if you have severe dizziness or feel like you might pass out.

You may feel very dizzy when you first wake up. Be careful when standing or sitting up from a lying position.

Your blood pressure will need to be checked often. Visit your doctor regularly. Keep using this medicine as directed, even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.

Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, heavy sweating, heart disease, dialysis, a low-salt diet, or taking diuretics (water pills). Tell your doctor if you have a prolonged illness that causes diarrhea or vomiting.

Alpha blocker: A drug that blocks receptors in arteries and smooth muscle. This action relaxes the blood vessels and leads to an increase in blood flow and a lower pressure for the control of hypertension. The action in the urinary tract enhances urinary flow in prostatic hypertrophy (enlarged prostate).

SAFETY INFORMATION

You should not use this medication if you are allergic to prazosin or similar medicines such as alfuzosin (Uroxatral), doxazosin (Cardura), silodosin (Rapaflo), tamsulosin (Flomax), or terazosin (Hytrin). Prazosin may cause dizziness or fainting, especially when you first start taking it or whenever your dose is changed. Be careful if you drive or do anything that requires you to be alert. Avoid standing for long periods of time or becoming overheated during exercise and in hot weather. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Prazosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using this medication. Do not stop using prazosin before surgery unless your surgeon tells you to.

Tell your doctor about all other medications you use, especially other blood pressure medications including diuretics (water pills).

Prazosin may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

FDA pregnancy category C. It is not known whether prazosin will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication. Prazosin can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

SIDE EFFECTS

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Call your doctor at once if you have a serious side effect such as:

fast or pounding heartbeats or fluttering in your chest;

feeling like you might pass out;

trouble breathing;

swelling in your hands, ankles, or feet; or

penis erection that is painful or lasts 4 hours or longer.

Less serious side effects may include:

mild dizziness;

weakness, tired feeling, drowsiness;

headache; ornausea.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.